What do you mean by "continuous impedance measurement"? An impedance measurement using the ADuCM350 is a discrete measurement. The excite channel applies a sine wave to the sensor/load, which induces a current. This current is measured by the TIA and the resulting voltage is sampled by the ADC. The DFT block takes 2048 of these samples to produce a real and imaginary value for the sensor/load impedance. To get another result, the same measurement must be repeated. So if you wish to continuously measure impedance, can you not just put a single measurement in a loop?